On building sites and construction areas, land levelling and earthmoving processes are often performed by bulldozers. These are equipped with continuous tracks for providing a stable attitude relative to the ground and a dozer blade for shoving sand, soil and debris. For land levelling usually a straight blade is used, which is relatively short and does not have a lateral curve or side wings.
Bulldozers have a disadvantage compared to wheel loaders, though, as the operating costs are higher. For instance, the transfer of bulldozers to the worksite is expensive, as even for short distances bulldozers need to be carried to the worksite, e.g. on articulated vehicles, whereas wheeled heavy machinery such as a wheel loader normally can be driven on its own wheels on public roads.
Therefore, an increasing number of wheel loaders are being used on construction sites for grading operations and allied fields. On the other hand, the use of wheel loaders for precise land levelling and earthmoving processes is complicated and challenging for the operator if a predefined working plane is to be maintained. Due to their wheels, wheel loaders generally have a higher center of gravity than bulldozers. Also, the dampers work independently at the two axles. Thus, the working axis of a wheel loader is subject to higher acceleration oscillations and other variations, for instance if heavy load on the loader bucket or blade shifts the center of gravity towards the front. Additionally, there is the possibility of wheel spin leading to a submerging of one or more wheels beneath the working plane. Thus, for an operator it is almost impossible to keep the tool of the loader in the correct position and orientation relative to the working plane all the time throughout the process.
Thus, there is a need a machine control system for precise land levelling and earthmoving processes aiding the operator to always hold the tool in the correct position and orientation—in particular the correct height and tilt angle—relative to the working plane.
There are some machine control aiding systems for heavy machinery equipment known from prior art that measure the position and/or orientation of a tool relative to the machinery and either provide a feedback for the operator about the position and attitude or at least partially operate the machinery automatically. For instance, U.S. 2006/0245902 A1 discloses a system identifying an orientation of a loader bucket and an indication of said orientation to an operator, and EP 1 988 220 A2 discloses a machine control system for wheel loaders and other heavy machinery equipment adapted to automatically relocate the tool into predefined positions.
The available systems are not suitable, though, for the special needs of precise land levelling and earthmoving processes with a wheel loader and a blade that can be used for land levelling or earthmoving purposes in a predefined working plane.